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Publication numberUS3849002 A
Publication typeGrant
Publication dateNov 19, 1974
Filing dateMay 11, 1973
Priority dateMay 11, 1973
Publication numberUS 3849002 A, US 3849002A, US-A-3849002, US3849002 A, US3849002A
InventorsHach C
Original AssigneeHach Chemical Co
Export CitationBiBTeX, EndNote, RefMan
External Links: USPTO, USPTO Assignment, Espacenet
Method and apparatus for eliminating air during fluid turbidity measurement
US 3849002 A
Method and apparatus for eliminating air in fluid samples continuously flowing through a closed turbidimeter instrument wherein the fluid flowed at a predetermined rate is directed through an air trap zone isolated from the turbidity sensing zone, a fluid is maintained in the air trap zone by means of the flow rate for a sufficient time period and through an elongated path to remove air bubbles present in the fluid.
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Description  (OCR text may contain errors)

Unite States Ptent Hach [ Nov. 19, 1974 METHOD AND APPARATUS FOR ELIMINATING AIR DURING FLUID TURBIDITY MEASUREMENT References Cited UNITED STATES PATENTS 57 2/1967 l-lach 356/208 3,560,099 2/1971 Boe et al 356/246 Primary Examiner-Vincent P. McGraw Attorney, Agent, or Firm-Wolfe, Hubbard, Leydig, Voit & Osann, Ltd.

[57] ABSTRACT Method and apparatus for eliminating air in fluid samples continuously flowingthrough a closed turbidimeter instrument wherein the fluid flowed at a predetermined rate is directed through an air trap zone isolated from the turbidity sensing zone, a fluid is maintained in the air trap zone by means of the flow rate for a sufficient time period and through an elongated path to remove air bubbles present in the fluid.

6 Claims, 2 Drawing Figures III II IIIIIIIIIIIIIII III 2-2 in FIG. 1.

The invention relates generally to methods and apparatus for'measuring the turbidity of fluids, known as turbidimeters, and concerns more particularly a method and apparatus for eliminating any influence of air from turbidity measurements in photoelectric turbidimeters for testing continuously flowing fluid samples.

Turbidity is an expression of the optical property of a fluid sample which causes light to be scattered and absorbed rather than passing in straightlines through the sample and it is a commonly accepted criterion for, by way of example, the quality of treated water. Turbidity is caused by the-presence of suspended matter or particles in fluids and as such may be sensed by the instruments known as turbidimeters which measure turbidity in terms of light reflected from a light beam introduced into the fluid by employing a sensing device such as a photocell to measure either the amount of light allowed to pass through the fluid or the amount of light reflected from the particles in the fluid.

The sensitivity of photoelectrical turbidimeters is quite high so that when testing continuously flowing fluid samplesithe presence of air bubbles in the fluid can' cause a false or phantom reading by the instruments. Entrained air which may occur due to the pumping or flow systems that carry the fluid into the turbidimeter heretofore has been a considerableproblem in its effect upon readings obtained.

Accordingly, it is a primary aim of the present invention to providea method and apparatus for eliminating entrained air. in fluid samples continuously flowing through closed turbidimeter instruments.

. A more specific object of the present invention is to provide an improved air elimination arrangement adapted for'utilization in connection with a continuous flow turbidimeter in which air bubbles present in the fluid entering the instrument are substantially removed before fluid turbidity is sensed photoelectrically so that measurements taken by theinstrument are not affected by the presence of such suspended air bubbles.

It is another object to provide a method and apparatus for eliminating air in turbidity instruments which is simple and economical for producing more reliable and accurate results with such instruments.

Other objects and advantages of the invention will become apparent upon reading the following detailed description and upon reference to the drawings.

BRIEF DESCRIPTION .OF THE DRAWINGS FIG. 1 is a vertical section of an exemplary turbidime'ter constructed in accordance with the present invention and employing the method of the invention;

FIG. 2 is a section taken approximately along the line DESCRIPTION OF THE PREFERRED EMBODIMENT While the invention will be described in connection vention'to the particular embodiment or procedure. On the contrary, I intend to cover all alternatives, modifications and equivalents as may be included within the spirit and scope of the appended claims.

Referring now to FIG. 1, there is shown an illustrative turbidimeter embodying the invention and arranged to eliminate air bubbles in the supplyof fluid introduced to the instrument prior to measurement of the turbidity in accordance'with the invention. For details of turbi-- dimeter instruments of the type to which the present invention is concerned, reference is made to C. C. Hach US. Pat. Nos. 3,306,157; 31,309,956; 3,528,750 and 3,564,262, all assigned to the assignee of the present invention.

Briefly, the turbidimeter is of the photoelectric type in which the turbidity of the fluid is tested by passing a beam light into afluid sample and measuring the effect of the light beam in terms of light energy striking photoelectric cells 12. The turbidimeter 10, as shown,

' includes an elongated container 14 having an inlet conduit 16 through which a supply of fluid is continuously introduced maintaining a vertical column 18 of fluid to be tested. For thepurpose of allowing the fluid to freely drain from the container, there is provided an upper drain opening 20 positioned vertically above the inlet conduit 16.

Supported at the top, of the-container 14, which in the preferred embodiment is tubular in form, there is an enclosed electrical head assembly 22 that may contain a suitable power supply (not shown) for a lightsource such as a precision, constant intensitylamp 24 shown supported by a bracket 26 above the fluid column 18.

Due to the fact'that the output of the turbidimeter is electrical, a recording instrument 28 which may he a galvanometer, a continuous recorder or other electrically energized instrument well known to those skilled in the art is provided to receive the output and, transform it into a desired useful state.

In order to direct the beam of light down through the fluid sample, there is provided a focusing lens 30 supported by a bracket 32 between the lamp 24 and the upper surface 34 of fluid column I8.

Photoelectric cells 12 are suspended in an annular array within the water column 18, but out of the direct path of the light beam as represented by the rays 36 directed down the center of the column.

In operation, the light beam as represented by the rays 36 passing down through the fluid column 18 are partially reflected in a certain proportion as illustrated by rays 38 by turbidity particles suspended in the fluid. The greater the number of particles present, the more turbid the fluid and thus the more light energy reflected. Consequently, the electrical output of the photoelectric cells 12 is-directly dependent upon the reflected light or turbidity of the fluid in the column 18.

a In accordancewith the present invention, the container 14 is constructed with an air-trap zone being providedtherein which allows for trapping and bleeding off air from fluid passing into the container at inlet conduit 16. More specifically, the air trap zone 40 is deflned by a centrally disposed cylindrical member 42 stripping of air from the fluid bysurface contact, there is provided a plurality of spaced annular baffles 46 radially projecting outward from the cylinder 42. Consequently, any air. present in the fluid flowing into the air trap zone 40 bubbles up through the fluid to the top of the air trap zone 40 as the fluid enters and as it moves past the baffles 46 toward the bottom 48 of the container 14.

For permitting the-escape of the removed air, there is provided a vent conduit 50 connected to the closure flange 44 with the vent conduit extending above the water level 34 to allow the free air passage out of the drain 20. y

In order to insure that a maximum amount of air is removed from the fluid to be tested prior to its movement into the measuring zone adjacent the photoelectric cells 12 in accordance with the method of the invention, the flow rate is maintained fairly slow to give the fluid ample time in the air trap zone 40 with the fluid reaching a fairly quiescent flow state in the lower zone 48 of the container and as it flows up through the central fluid column 18 before exiting through drain 20. Thus, the fluid entering the container 14 is maintained at a prolonged period in the air trap zone away from the turbidityqdetecting or measuring zone and then it is flowed through an elongated path which permits a more quiescent flow of the fluid to set in before the turbidity testing takes place.

I claim as my invention:

I. In a turbidimeter for sensing the turbidity of a continuously flowing fluid sample including a container for supporting a vertical column of fluid to be tested, means defining a drain opening in said container for establishing an upper surface on said fluid column whereby the fluid may drain from the column at the level of said upper surface, inlet means for transmitting a continuous flow of fluid to said column, a light source fixed relative to said container for directing a beam of light down into said fluid column, means including photoelectric cells surrounding said light beam and being disposed facing the beam passing through the fluid column to define a measuring zone, the electrical output of said cells being dependent upon the amount of light energy from said light beam that is reflected toward the photoelectric cells by particles suspended in said fluid, the improvement comprising, an air trap zone disposed between the inner wall of the container and the central portion of the fluid column through which said light beam passes, said air trap zone being in communication with the inlet means transmitting said fluid flow to the column, vent means connecting said air trap zone to said drain outlet, and said air trap means extending downwardly a substantial distance along the length of said container so that fluid flowing through said air trap zone is present a sufficient length of time to eliminate air and reach a quiescent state prior to flowing up through the central column to the measuring zone and departure of said fluid through said drain.

2. The turbidimeter as claimed in claim 1 wherein said air trap means comprises a cylindrical member having a radial flange at its upper end extending to the inner peripheral wall of said container and a plurality of spaced annular baffles surrounding and projecting from said cylindrical member.

3. The turbidimeter as claimed in claim 2 wherein said photoelectric cells are disposed beneath the surface of said fluid and above said flange end of said cylindrical member.

4. A turbidimeter as claimed in claim 2 wherein said vent means comprises a conduit connected to said flange end of the tubular means and said conduit extends above the surface of the fluid column.

5. A method of sensing the turbidity of a fluid sample in a turbidimeter having a chamber including inlet and outlet means and a sensing'zone including means for measuring light energy reflected from a beam of light passed through a fluid column in said chamber comprising the steps of, (a) flowing the fluid continuously to the turbidimeter inlet at a predetermined rate, (b) directing said fluid flow through an air trap zone isolated from said sensing zone, (c) maintaining said fluid in the air trap zone by means of said flow rate for a sufficient time period to remove air bubbles present in said fluid and (d) directingsaid fluid free of entrained air through an elongated path sufflcient to reach a quiescent flow of said fluid to the sensing zone for the turbidity test prior to exiting of said fluid through the outlet.

6. A method as claimed in claim 5 including venting said air trap zone and passing said removed air to the

Patent Citations
Cited PatentFiling datePublication dateApplicantTitle
US3306157 *Nov 19, 1962Feb 28, 1967Hach Chemical CoTurbidimeter for sensing the turbidity of a continuously flowing sample
US3560099 *Jul 7, 1969Feb 2, 1971Inst ProduktudviklingColorimeter flow cell including a baffle to remove gas bubbles
Referenced by
Citing PatentFiling datePublication dateApplicantTitle
US4070263 *Sep 9, 1976Jan 24, 1978DegremontApparatus for the measurement of the mobility of colloids in an electric field
US4294542 *Dec 17, 1979Oct 13, 1981Weyerhaeuser CompanyMethod and apparatus for counting small objects suspended in a liquid stream
US4740709 *Apr 10, 1986Apr 26, 1988The United States Of America As Represented By The Department Of Health And Human ServicesMethod of sensing fluid properties independent of bubble concentrations
US5059811 *Aug 30, 1990Oct 22, 1991Great Lakes Instruments, Inc.Turbidimeter having a baffle assembly for removing entrained gas
US5335067 *Sep 29, 1992Aug 2, 1994The United States Of America As Represented By The United States Department Of EnergySpectrophotometric probe
US6210640Jun 8, 1998Apr 3, 2001Memc Electronic Materials, Inc.Collector for an automated on-line bath analysis system
US7686927Aug 25, 2006Mar 30, 2010Novellus Systems, Inc.Methods and apparatus for controlled-angle wafer positioning
US8507262 *Feb 23, 2007Aug 13, 2013Cytoprom LtdApparatus and method for monitoring cultures
US8962085Jan 8, 2010Feb 24, 2015Novellus Systems, Inc.Wetting pretreatment for enhanced damascene metal filling
US20100233751 *Feb 23, 2007Sep 16, 2010Medical Research CouncilApparatus and method for monitoring cultures
WO1999064838A1 *Jun 4, 1999Dec 16, 1999Memc Electronic MaterialsCollector for an automated on-line bath analysis system
U.S. Classification356/339, 356/246
International ClassificationG01N1/28
Cooperative ClassificationG01N1/28
European ClassificationG01N1/28